L17 bacterial nutrition

Question 1

Bacterial Metabolism is relevant because it

Answer 1

–defines the preferred environment

–facilitates identification

–reveals methods for killing or suppressing bacteria

Question 2

Clostridium botulinum exotoxin

Answer 2

causes disease since the bacteria does not grow well in the body, can spread from a site of infection or improperly prepared food

Question 3

Clostridium perfringens

Answer 3

produces enterotoxin which does not usually severely harm the host however it allows for the spread of spores through diarrhea

Question 4

TYPE III SECRETORY SYSTEM

Answer 4

an organelle of virulence found in gram negative bacteria.
injects virulence factors into host cells, the virulence factors can then reprogram and compromise many aspects of the host cell.

Question 5

Pure culture technique

Answer 5

Fundamental method of analyzing bacteria. differences
between colonies allow many pathogens to be identified. Bacteria are spread so that individual bacteria grow in distinct colonies. Different species have different colony morphologies

Question 6

variables affecting growth rate of bacteria

Answer 6

1. The nature of the culture medium and the presence of any appropriate supplemental nutrients
2. The presence or absence of oxygen
3. The temperature

Question 7

4 phases of growth in liquid culture

Answer 7

1. lag phase - no growth
2. exponential phase - consistent growth (max as quick as 20min)
3. Stationary phase - growth=death
4. death phase - death > growth

Question 8

DNA gyrase

Answer 8

normally relieves coiling during DNA replication, differ between eukaryotes and prokaryotes therefore are a good target for drugs such as -novobiocin and synthetic quinolones which inhibit gyrase.

Question 9

Protein synthesis

Answer 9

Amino acids are joined together in a chain according to
instructions provided by mRNA. This occurs within the ribosome, a complex molecular machine composed of RNA and protein.

The ribosome is the target of a very large group of antibiotics, including erythromycin, tetracycline’s, streptomycin and spectinomycin.

Question 10

Peptidoglycan synthesis

Answer 10

Production and assembly occurs in three separate
compartments in the cell.
a. The subunits of peptidoglycan are synthesized in the cytoplasm.
b. These subunits are transferred across the membrane by a carrier molecule.
c. The newly transferred subunits are cross linked to the peptidoglycan already present on the other side of the membrane.

drugs inhibit peptidoglycan synthesis at any of the above stages

Question 11

penicillin-binding proteins

Answer 11

make and break these crosslinks during peptidoglycan maturation, an activity that is critical to cell growth.

are inhibited by penicillin.

Question 12

A pathogens process of metabolism can tell you

Answer 12

1. its requirements for energy production and therefore preferred environment and where an infection is most likely to occur
2. identification based on preferred energy sources
3. production of toxic by-products during respiration (oxygen radicals) and so they must also produce protective enzymes (peroxidase, superoxide dismutase)

Question 13

3 major steps in the production of energy

Answer 13

1. nutrient molecules enter the cell
2. they are broken down and partially converted to energy
3. fermentation or respiration -removes more energy

Question 14

Siderophores

Answer 14

molecules secreted by bacteria that trap iron, and which can be transported back into the bacterium. Some siderophore genes are on plasmids and these plasmids are virulence factors.

(iron is required for many bacterias to grow)

Question 15

Central metabolic pathways

Answer 15

the initial breakdown of nutrient molecules,
occurs before respiration (electron transport and then
oxidative phosphorylation) or fermentation.

Question 16

Respiration

Answer 16

highly efficient stepwise removal of energy (electron transport) that can be used to generate a gradient of protons across the bacterial membrane (oxidative phosphorylation).

The gradient can be used to power transport of molecule or rotation of the flagellum among other things.

Any drug treatment that impairs the integrity of the cell
envelope can destroy the gradient and kill the cell.

Question 17

Fermentation

Answer 17

less efficient then respiration

produces organic molecules that can be used to diagnose the infecting orgamism

Question 18

peroxidases

Answer 18

remove hydrogen peroxide from cells, a reactive oxygen species

Question 19

superoxide dismutase

Answer 19

removes the supraoxide ion a reactive oxygen species

Question 20

types of adaptive responses

Answer 20

1. Spore formation. EX- by Bacilli and Clostridia are a response to a lack of nutrient by the formation of a dormant, resistant cell type. Spores can enhance or even be crucial for pathogenesis.
2. Heat shock response, during which protective factors that allow the cells to survive increased heat and other stresses are synthesized. Heat shock conditions are probably commonly encountered during pathogenesis.
3. SOS system which is induced to repair DNA damage when mutagenic conditions are encountered.

Question 21

major targets of antibiotics

Answer 21

peptidoglycan synthesis
DNA
RNA polymerase
cell membrane
ribosomes